The present invention relates to beam scanners in general, and, more particularly, to a high speed beam scanner for use in drum-type laser imagesetters.
High resolution drum-type laser imagesetters require low wobble, low noise and first surface spin mirror with minimal optical aberrations. As the electronic imaging market demands faster and faster scan speeds, a variety of problems arise with increased scan speed. First, the inherent nature of the spinners' 45 degree surface increases windage and noise when the speed is increased. Windage is considered to be a forcing function for air-bearing wobble, and the audible noise becomes a work environment concern at high rotational speeds. Additionally, any increase of the pumping of ambient air across the spin mirror surface increases both erosion and chemical degradation. This is especially true for highly polluted areas.
It is a general object of the present invention to provide an improved high speed beam scanner.
It is a specific object of the invention to reduce acoustic noise associated with a high speed rotating beam deflector.
It is another object of the invention to reduce windage in the high speed rotation beam deflector.
It is still another object of the invention to prevent deleterous effects upon the rotating beam deflector caused by environmental conditions external to the rotating beam deflector.
It is a further object of the invention to enclose the rotating deflector in a hollow shield having beam entrance and exit apertures.
It is a still further object of the invention to environmentally seal the exit aperture with a flat window.
It is yet another object of the invention to prevent edge distortion of the flat window during rotation of the hollow shield.